use std::sync::atomic::{AtomicUsize, Ordering};
use std::collections::HashMap;
use std::sync::{Arc, Mutex};

/// 对象池优化
pub struct ObjectPool<T> {
    pool: Mutex<Vec<T>>,
    max_size: usize,
}

impl<T: Default + Clone> ObjectPool<T> {
    pub fn new(max_size: usize) -> Self {
        ObjectPool {
            pool: Mutex::new(Vec::with_capacity(max_size)),
            max_size,
        }
    }
    
    pub fn acquire(&self) -> T {
        let mut pool = self.pool.lock().unwrap();
        pool.pop().unwrap_or_default()
    }
    
    pub fn release(&self, item: T) {
        let mut pool = self.pool.lock().unwrap();
        if pool.len() < self.max_size {
            pool.push(item);
        }
    }
}

/// 缓存优化的值类型
#[repr(C, align(64))]
pub struct CacheOptimizedValue {
    pub value: i64,
    _padding: [u8; 56],
}

impl CacheOptimizedValue {
    pub fn new(val: i64) -> Self {
        CacheOptimizedValue {
            value: val,
            _padding: [0; 56],
        }
    }
}

/// 字符串驻留池
pub struct StringInterner {
    strings: Mutex<HashMap<String, Arc<str>>>,
}

impl StringInterner {
    pub fn new() -> Self {
        StringInterner {
            strings: Mutex::new(HashMap::new()),
        }
    }
    
    pub fn intern(&self, s: String) -> Arc<str> {
        let mut strings = self.strings.lock().unwrap();
        if let Some(existing) = strings.get(&s) {
            existing.clone()
        } else {
            let arc_str: Arc<str> = s.into();
            strings.insert(arc_str.to_string(), arc_str.clone());
            arc_str
        }
    }
}

/// 分代GC优化
pub struct GenerationalGC {
    young_gen: Vec<usize>,
    old_gen: Vec<usize>,
    young_threshold: usize,
    old_threshold: usize,
    survived_count: HashMap<usize, usize>,
}

impl GenerationalGC {
    pub fn new() -> Self {
        GenerationalGC {
            young_gen: Vec::new(),
            old_gen: Vec::new(),
            young_threshold: 1000,
            old_threshold: 10000,
            survived_count: HashMap::new(),
        }
    }
    
    pub fn allocate(&mut self, obj_id: usize) {
        self.young_gen.push(obj_id);
    }
    
    pub fn minor_gc(&mut self) {
        // 只清理新生代
        let mut to_promote = Vec::new();
        
        for &obj in &self.young_gen {
            if self.is_reachable(obj) {
                *self.survived_count.entry(obj).or_insert(0) += 1;
                
                if self.survived_count[&obj] > 3 {
                    to_promote.push(obj);
                }
            }
        }
        
        // 晋升到老年代
        for obj in to_promote {
            self.old_gen.push(obj);
        }
        
        self.young_gen.clear();
    }
    
    fn is_reachable(&self, _obj_id: usize) -> bool {
        // 简化的可达性检查
        true
    }
}

/// 内存预分配器
pub struct MemoryPreallocator {
    blocks: Vec<Vec<u8>>,
    block_size: usize,
    current_block: usize,
    offset: usize,
}

impl MemoryPreallocator {
    pub fn new(block_size: usize, block_count: usize) -> Self {
        let mut blocks = Vec::new();
        for _ in 0..block_count {
            blocks.push(vec![0; block_size]);
        }
        
        MemoryPreallocator {
            blocks,
            block_size,
            current_block: 0,
            offset: 0,
        }
    }
    
    pub fn allocate(&mut self, size: usize) -> Option<*mut u8> {
        if self.offset + size > self.block_size {
            self.current_block += 1;
            self.offset = 0;
            
            if self.current_block >= self.blocks.len() {
                return None;
            }
        }
        
        let ptr = unsafe {
            self.blocks[self.current_block].as_mut_ptr().add(self.offset)
        };
        
        self.offset += size;
        Some(ptr)
    }
}

/// 性能计数器
pub struct PerformanceCounter {
    allocations: AtomicUsize,
    deallocations: AtomicUsize,
    gc_cycles: AtomicUsize,
    cache_hits: AtomicUsize,
    cache_misses: AtomicUsize,
}

impl PerformanceCounter {
    pub fn new() -> Self {
        PerformanceCounter {
            allocations: AtomicUsize::new(0),
            deallocations: AtomicUsize::new(0),
            gc_cycles: AtomicUsize::new(0),
            cache_hits: AtomicUsize::new(0),
            cache_misses: AtomicUsize::new(0),
        }
    }
    
    pub fn increment_allocations(&self) {
        self.allocations.fetch_add(1, Ordering::Relaxed);
    }
    
    pub fn increment_deallocations(&self) {
        self.deallocations.fetch_add(1, Ordering::Relaxed);
    }
    
    pub fn increment_gc_cycles(&self) {
        self.gc_cycles.fetch_add(1, Ordering::Relaxed);
    }
    
    pub fn record_cache_access(&self, hit: bool) {
        if hit {
            self.cache_hits.fetch_add(1, Ordering::Relaxed);
        } else {
            self.cache_misses.fetch_add(1, Ordering::Relaxed);
        }
    }
    
    pub fn get_stats(&self) -> (usize, usize, usize, f64) {
        let allocs = self.allocations.load(Ordering::Relaxed);
        let deallocs = self.deallocations.load(Ordering::Relaxed);
        let gcs = self.gc_cycles.load(Ordering::Relaxed);
        let hits = self.cache_hits.load(Ordering::Relaxed);
        let misses = self.cache_misses.load(Ordering::Relaxed);
        
        let hit_rate = if hits + misses > 0 {
            hits as f64 / (hits + misses) as f64
        } else {
            0.0
        };
        
        (allocs, deallocs, gcs, hit_rate)
    }
}